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SEMI 30.1-0200 © SEMI 1998, 2000 42 than relative to th e substrate shape and dimensions. ISEM als o defines th e M20P coordinate sys te m to be one which is designed to b e “parallel” to the SEMI M20 coordinate sy stem.…

SEMI 30.1-0200 © SEMI 1998, 200041

method relative either to the substrate pattern

coordinate system or to another pattern-element

coordinate system. The pattern-element coordinate

system shall be a right-hand Cartesian coordinate

system which is designed to be parallel to the

substrate pattern coordinate system. The pattern-

element coordinate system shall be identified by a

name. The location of its origin and axis relative to

the substrate pattern coordinate system shall be

communicated in terms of the substrate pattern

coordinate system.

NOTE: For wafers, this method is based on SEMI M21,

and the coordinate system is named “M21” and its origin

and axis relative to the “M20P” coordinate system are

given in terms of the M20P coordinates.

• ISEM requires that equipment have the capability

to use site location information that is based on the

user’s product designs, which the user shall

provide in the appropriate ISEM-required format.

• ISEM-compliant equipment shall have the

capability to define, locate, and report site

information using only the ISEM-defined right-

handed Cartesian coordinate system formats. This

requirement does not preclude equipment from

having additional capability for defining or

reporting site location information using other

formats.

• Coordinate system name and placement relative to

the “higher” coordinate system shall be defined and

communicated using the following ISEM data

items, in terms of either expected or actual

placement: CoordSys, XlateData, and their

included data items.

• Alignment site information shall be defined and

communicated using the following ISEM items:

the variable item AlignList, the “ALIGNLIST”, the

Process program class of “TABLE-ALIGN-DEF”,

and their included information.

• Areas to be inspected shall be reported using the

specific coordinate system defined by the user. The

following ISEM items are used to define and

communicate area locations: the variable item

“AREALIST”, the “AREALIST”, and the Process

program class of “TABLE-AREA-DEF”, and their

included information.

• The displacement of an actual coordinate system

relative to its expected location shall be

communicated using the ISEM data item:

XlateData and its included data items.

• The displacement of an actual site location relative

to its expected site location shall be communicated

using the ISEM data item: Offset and its included

data items.

• The equipment vendor shall document the

requirements for the ISEM data items used in

alignment of a coordinate system.

• The equipment vendor shall provide and document

a means for the user to define and communicate a

pattern map using SEMI M21 data. A pattern map

defines the layout of equal-sized rectangular

pattern-elements which make up a pattern. Each

pattern-element shall have a name, using the SEMI

M21 naming convention.

NOTE: For patterned wafers, the naming method shall

be that described in SEMI M21, and the pattern-element

information shall be communicated using the ISEM data

item of SEMI M21Data.

• For ISEM compliance, inspection equipment shall

report various anomaly data; AnomalyID,

coordinates, and attributes. Review equipment shall

receive this data for anomalies and be able to locate

them and perhaps modify the coordinates.

Anomaly coordinates shall be reported using ISEM

table named “TABLE-ANOMALY-DEF” and its

included data.

R1-3 Coordinate System for a Substrate

R1-3.1 SEMI M20 Coordinate System — The SEMI

M20 standard (Specification for Establishing a Wafer

Coordinate System) describes how to map a right-

handed Cartesian coordinate system to a substrate so

that its origin is at the center of the substrate, and its

negative y-axis bisects the substrate’s primary fiducial.

This coordinate system is defined by ISEM to be the

“M20” coordinate system. The only information

required by equipment in order to establish an “M20”

coordinate system is the substrate size and the type of

fiducial, which are communicated using the ISEM data

items named SubstrateSize and Fiducial. Another

ISEM data item named Orientation identifies how the

substrate is loaded on the equipment. Note that the

SEMI M20 standard requires that the “M20” coordinate

system is fixed on the substrate and is not affected by

how the substrate is loaded on equipment. Also, as

stated in the SEMI M20 standard, an orientation of “0”

degrees designates a substrate loaded on equipment,

with the primary fiducial towards the operator or

“down.”

R1-3.2 M20P Coordinate System — ISEM defines the

M20P coordinate system to be one which is aligned to

the pattern on the substrate. The M20P coordinate

system is useful because in many cases, it is more

significant to the user to know the location of an

anomaly relative to the pattern on the substrate rather

SEMI 30.1-0200 © SEMI 1998, 2000 42

than relative to the substrate shape and dimensions.

ISEM also defines the M20P coordinate system to be

one which is designed to be “parallel” to the SEMI M20

coordinate system. In practice, because of experimental

errors, both the origins and the axes may differ slightly

from their intended values of a simple translation and

no rotation. Equipment should be designed to be able to

locate the alignment sites, given the various possible

experimental errors.

R1-3.3 Establishing an M20P Coordinate System — A

minimum of two alignment sites is necessary to

establish an M20P coordinate system on a substrate.

Additional sites are often used to determine a scaling

ratio of the dimensions of the actual coordinate system

relative to the dimensions of the expected coordinate

system and are reported using the ISEM data item of

ScaleFactor.

XlateData is used to report actual coordinate system

location. Most equipment cannot distinguish whether

patterned substrate site location errors are due to the

substrate, the layout on the substrate, or the

equipment’s ability to locate the sites. However,

information that is available through the use of

patterned-substrate alignment sites can provide a means

for identifying potential equipment problems. For

instance, assume that the only pattern-layout location

error on a substrate is that due to the establishment of

the location of the substrate center and fiducial. For

many users and equipment systems, this is a good

assumption. If this is the case, then the ISEM data item

named XlateData can be used to track this error.

Although the error may result from multiple sources,

being able to track it on various equipment will enable

users to apply statistical process control techniques to

identify the specific sources.

Offset sites may be found by equipment at actual

locations which deviate from their expected locations

through either pattern layout errors or equipment

“stage” or imaging errors. Again, in a controlled

manufacturing process, these combined errors should

be normally distributed, and non-normal deviations

may indicate possible equipment problems. The actual

position of a site relative to its expected position shall

be reported through the use of the ISEM data item

named Offset.

R1-4 Layout of Rectangular Pattern Elements

on a Substrate Using SEMI M20 Coordinate

System

Equipment shall be capable of routine, automated

operation without needing substrate layout information

(e.g., field or die maps). However, having the capability

to provide substrate layout information to equipment

from the host can be desirable. ISEM defines a means

to do this in this section for substrates, based on SEMI

M21 (Specification for Assigning Addresses to

Rectangular Elements in a Cartesian Array.) The SEMI

M21 standard is limited to defining how to assign

“addresses” to elements and how to find the “array

center” element. It does not specify how the rectangular

pattern-elements are located on the substrate. In this

section, ISEM defines how these pattern-elements are

located on a substrate, using the data item named

M21Data, and how to establish within-element

coordinate systems. Any additional layout information,

such as within-element structure details or element

attribute information, is beyond the scope of ISEM.

R1-4.1 ISEM “M21” Layouts

• An “M21” layout consists of an array of equal-

sized rectangular pattern-elements with no space

between the pattern elements.

• ISEM defines the “M21” layout on a substrate to

include all pattern-elements which are either

wholly or partially within the circumference of the

substrate.

• The ISEM approach is to define the pattern map by

specifying the M20P coordinate for the lower left

corner of the minimum number of pattern-elements

needed to define the layout, along with the pattern-

element addresses (names). For a non-tiled layout,

the location and name of a single pattern-element is

sufficient to establish the “M21” layout. For tiled

layouts, the location and name of one pattern-

element in each row or column are required. Note

that the location of the lower left corner of some

pattern-elements may be outside the circumference

of the substrate.

• The “M21” pattern-element coordinate system

shall have its x and y axes parallel to the respective

M20P coordinate system axes and shall have their

origins at the lower left corner of each element.

The pattern-element coordinate system shall have a

name and a specific pattern-element address

identifier per SEMI M21.

• Layout definition is supported only for host-to-

equipment communications. The user is

responsible for ensuring that the pattern-element

addresses provided to the equipment agree with the

SEMI M21 specification. The equipment need not

check this, other than to ensure that there are not

conflicts within the provided layout, and shall

report results with pattern-element addresses as

provided by the user.

• “M21” layouts are established within the M20P coordinate system and need not require any additional

alignment site data than is needed to establish the M20P coordinate system. However, as with M20P, additional

alignment may be necessary because of errors in either the pattern layout or the equipment’s ability to locate

features. Offset shall be used to report the location corrections that result from any within-element alignments.

R1-5 How an M20P Coordinate System Is Established on a Substrate

The following example is fairly basic. For this example, the M20P coordinate system has a zero translation from the

SEMI M20 coordinate system. Also, the equipment documentation states that 4 alignment sites are required. The

equipment does M20P alignment on two alignment sites and does a low resolution and then a high resolution

alignment at each site. Note that the specific alignment point is different at the two resolutions, so the coordinates

are slightly different. The alignment sites are defined to the equipment via the process program class named

“TABLE-ALIGN-DEF”, as detailed below. The order of the sites in “TABLE-ALIGN-DEF” is not important. The

sites are then selected via the CPNAME named “ALIGNLIST”, which is included in the PP-SELECT command.

The order of the sites listed in “ALIGNLIST” is important and is as-specified in the equipment’s documentation.

The first item is the alignment site for the first low resolution site, the second item is for the first high resolution site,

the third item is the second low resolution site, and the fourth is the second high resolution site.

“TABLE-ALIGN-DEF”

AlignName Coordx Coordy Coordsys Attribute (1)

Coarse1 -60000 -200 “M20P”

Fine1 -60020 -205 “M20P”

Coarse2 +60000 +200 “M20P”

Fine2 +59980 +195 “M20P”

“ALIGNNAME”

L,4

1. <Coarse1>

2. <Fine1>

3. <Coarse2>

4. <Fine2>

Using this information, the equipment will go to the nominal “M20” location for Coarse1, then “find” where it

actually is. The offset between the nominal “M20” location and the actual “M20” location is then used to “find”

Fine1. The actual M20 location of Fine1 is saved. The process is then repeated for Coarse2 and Fine2. The

equipment can now determine the “M20” to M20P offset from the nominal and actual coordinates. First, a summary

of the data:

xN1 = -60020 yN1 = -205 Nominal x and y data for the first fine site

xA1 = -59800 yA1 = -150 Actual x and y data for the first fine site

xN2 = +59980 yN2 = +195 Nominal x and y data for the second fine site

xA2 = +60060 yA2 = +175 Actual x and y data for the second fine site